The reason that made Professor Holmes bring his energies and knowledge to bear upon this subject was somewhat curious. The siren in its first form made its way from the United States to Great Britain. The British Admiralty realized the power and penetration of its sound, and forthwith adopted it in the navy, operating it by steam instead of by air. At this there arose a great outcry from the mercantile marine. Captains argued that the similarity of the signals confused and often misled them, as they could not tell in the fog whether the sound proceeded from a warship or a lighthouse. The Board of Trade was forced to intervene, but, as it had no jurisdiction over the Admiralty, it sought to extricate itself from an awkward situation by inviting Professor Holmes to perfect a siren which would emit a distinctive sound. His efforts were crowned with complete success. [Illustration: FIG. 15.--THE FIXED (A) AND REVOLVING (B) PARTS OF THE SIREN.] Professor Holmes exhibited his wonderful device at the Paris Exhibition of 1867. He installed it in working order, and the visitors displayed an anxiety to hear it. It was brought into action, and those around never forgot the experience. It was the most diabolical ear-splitting noise which had been heard, and, apprehensive that serious results might arise from its demonstration when the buildings were thronged with sight-seers, the authorities refused to permit it to be sounded again. The humorous illustrated papers did not suffer such a golden opportunity to escape. Grotesque and laughable cartoons appeared depicting the curious effects produced by the blast of the instrument, one showing the various statues being frightened off their pedestals proving exceptionally popular.